20 February 2009 Time-of-flight application for fluid flow measurement
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Abstract
Fluidic measurement is a critical part of clinical care and homeostasis maintenance. This paper reports feasibility study of measuring flow velocities over a wide dynamic range using a non-contact measurement technique, optical time-of-flight (OTOF), with the objective of developing a compact instrument that can be used to measure fluid flow for IV medication delivery. In this study, a 1480nm laser diode focused to a 20μm spot introduces a heat bolus into the fluid. This localized temperature increase results in a correlated change in refractive index, detected downstream by observing defocusing of the visible beam, focused to a 10μm spot in the center of the fluid path. The OTOF measurement provides the centerline velocity of the fluid flow. CFD modeling ensured that laminar flow was fully developed; prior to the OTOF measurement point, thus providing a simple, empirical relationship between OTOF and fluid velocity, and hence volumetric flow rate. Measurements have been performed over a wide range of flow velocity from 1 mm/s to 1 m/s with approximately ±5% measurement error for broad ranges of fluid properties such as viscosity (0.77-13.88 cp), density (0.98-1.17 g/cm3) and temperature (5-35 °C). The dynamic range of measured velocity/flow rates is a function of the distance between the heating and the detection laser beams.
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Brian Markey, Yizhong Yu, Tamas Ban, Gagan Johal, "Time-of-flight application for fluid flow measurement", Proc. SPIE 7186, Optical Diagnostics and Sensing IX, 71860S (20 February 2009); doi: 10.1117/12.822772; https://doi.org/10.1117/12.822772
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